Extend vscode.extensions.getExtension to return extensions from other extension host

[jrieken]

Today, getExtension only returns extensions that are registered in the same extension host. This can be problematic when extensions enable/disable feature in the presence of other extensions.

slightly related: #84997

[thegecko]

Is the intent that this feature would add the ability to use extension APIs across extension hosts?

[jrieken]

Is the intent that this feature would add the ability to use extension APIs across extension hosts?

No, it is just about exposing metadata about extensions from other extension host but you will not (ever) be able to use their API (because there are guarantees that these API are IPC-safe)